When Michelle Gourley in Kaiapoi tried to telephone her father, John Gourley in Opawa to see how he was after the Christchurch earthquake, she could not get through.

Fearing that 70-year-old John had been injured or killed, she set off in her car to drive there. But, stuck in traffic, she called her sister Joanne in Auckland.

They both decided to call their brother Sean in San Francisco, who put a message on the Twitter social network asking the world if anyone was close to his father's house. Moments later a stranger replied: "Sean I'm near Opawa, what's address."

After being given the address, the stranger found John Gourley sitting in his car outside his badly damaged house. Michelle Gourley arrived three hours later and took him back to Kaiapoi.